U.S. patent application number 10/961154 was filed with the patent office on 2005-03-03 for fuel injection valve.
This patent application is currently assigned to UNISIA JECS CORPORATION. Invention is credited to Kato, Hideo, Kobayashi, Takayuki.
Application Number | 20050045748 10/961154 |
Document ID | / |
Family ID | 19189008 |
Filed Date | 2005-03-03 |
United States Patent
Application |
20050045748 |
Kind Code |
A1 |
Kobayashi, Takayuki ; et
al. |
March 3, 2005 |
Fuel injection valve
Abstract
A fuel injection valve has: a tubular body, a valve seat member,
a valve body, a core tube, a bias spring, and an electromagnetic
actuator. The core tube is press fitted into the tubular body. The
core tube has a first end side opposing an absorption section of
the valve body in such a manner as to form an axial gap interposed
between the first end side of the core tube and the absorption
section. The core tube has a second end side axially extending in
the tubular body to a certain position on a way to the second end
side of the tubular body. The axially extending second end side of
the core tube has an outer periphery which is formed with a reduced
diameter section for increasing an accuracy in positioning the core
tube when the core tube is press fitted into the tubular body.
Inventors: |
Kobayashi, Takayuki; (Gunma,
JP) ; Kato, Hideo; (Tochigi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
UNISIA JECS CORPORATION
|
Family ID: |
19189008 |
Appl. No.: |
10/961154 |
Filed: |
October 12, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10961154 |
Oct 12, 2004 |
|
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|
10194274 |
Jul 15, 2002 |
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6811104 |
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Current U.S.
Class: |
239/533.2 |
Current CPC
Class: |
F02M 61/168 20130101;
F02M 51/0682 20130101; F02M 51/0667 20130101 |
Class at
Publication: |
239/533.2 |
International
Class: |
F02M 059/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2001 |
JP |
2001-395543 |
Claims
1-20. (canceled).
21. A fuel injection valve, comprising: a stepped tubular body of a
magnetic material, including a larger body section, a smaller body
section smaller in sectional size than the larger body section, and
a step portion connecting the larger body section and the smaller
body section; a valve seat fixed to a forward end of the smaller
body section of the stepped tubular body; a stepped core tube
including a smaller tube section confronting the valve seat, and a
larger tube section press fit in the smaller body section of the
stepped tubular body, the larger tube section of the stepped core
tube being formed with a reduced portion located in the smaller
body section of the stepped tubular body; a valve element disposed
in the smaller body section of the tubular body, between the
smaller tube portion of the core tube and the valve seat; and an
electromagnetic actuator disposed outside the stepped tubular body,
and arranged to drive the valve element between the core tube and
the valve seat.
22. The fuel injection valve as claimed in claim 21, wherein the
reduced portion is formed in a second tube end of the stepped core
tube which extends from the second tube end to a first tube end
toward the valve seat.
23. The fuel injection valve as claimed in claim 22, wherein the
larger body section and the stepped portion of the stepped core
tube define a larger inside cavity sized to allow passage of the
stepped core tube from the larger body section into the smaller
body section, and the reduced portion of the larger tube section of
the stepped core tube defines an annular space which is formed
between the smaller body section and the reduced portion and which
is open to the larger inside cavity formed by the larger body
section and the step portion.
24 The fuel injection valve as claimed in claim 22, wherein the
stepped core tube is press fit in the smaller body section of the
stepped tubular body by being inserted into the stepped tubular
body from a second body end of the stepped tubular body which
extends in a longitudinal direction from the second body end to a
first body end that is the forward end of the smaller body section
in which the valve seat is fixedly disposed until the reduced
portion reaches the smaller body section beyond the step portion of
the stepped tubular body.
25. The fuel injection valve as claimed in claim 22, wherein the
smaller body section of the stepped tubular body has a cylindrical
inside wall surface; the larger tube section of the stepped core
tube has a cylindrical outside wall surface which is fit in the
cylindrical inside wall surface of the smaller body section of the
stepped tubular body; and the reduced portion of the larger tube
section has an outside circumferential surface confronting the
cylindrical inside wall surface of the smaller body section across
an annular space which is bounded between the cylindrical side wall
surface of the smaller body section of the stepped tubular body and
the outside circumferential surface of the reduced portion of the
larger tube section of the core tube.
26. The fuel injection valve as claimed in claim 25, wherein the
outside circumferential surface of the reduced portion extends from
a first surface end located at an end of the outside cylindrical
wall surface of the larger tube section of the stepped core tube,
to a second surface end located in the second end of the stepped
core tube.
27. The fuel injection valve as claimed in claim 22, wherein the
larger tube section includes a main portion having a cylindrical
outside surface, fit in the smaller body section of the stepped
tubular body, and the reduced portion has a cylindrical outside
surface whose diameter is smaller than a diameter of the cylinder
outside surface of the main portion of the larger tube section.
28. The fuel injection valve as claimed in claim 22, wherein the
cylindrical outside surface of the main portion of the larger tube
section extends from a second end to a first end toward the smaller
tube section; the cylinder outside surface of the reduced portion
extends from a second end located in the second end of the stepped
core tube, to a first end; and the reduced portion has an annular
step surface extending radially inwardly from the second end of the
cylindrical outside surface of the main portion of the larger tube
section to the first end of the cylindrical outside surface of the
reduced portion.
29. The fuel injection valve as claimed in claim 22, wherein the
reduced portion includes a tapered portion.
30. The fuel injection valve as claimed in claim 29, wherein the
larger tube section has an outside cylindrical surface which is
forcibly fit in the smaller body section of the stepped tubular
body and which extends from a second end to a first end in a
longitudinal direction of the stepped core tube; and the tapered
portion of the reduced portion extends from a second end located in
the second end of the stepped core tube to a first end located at
the second end of the cylindrical outside surface of the larger
tube section, and has a cross sectional size gradually decreasing
from the first end of the tapered portion to the second end of the
tapered portion.
31 The fuel injection valve as claimed in claim 22, wherein the
reduced portion of the stepped core tube is spaced inwardly from an
inside surface of the smaller body section so as to form an annular
space between the inside surface of the smaller body section and
the reduced portion and thereby to allow the smaller body section
to be deformed elastically into the annular space to prevent
movement of the stepped core tube in the smaller body section of
the stepped tubular body in a direction toward the larger body
section.
32. The fuel injection valve as claimed in claim 22, wherein the
fuel injection valve further comprises a spring retainer fixed in
the stepped core tube, and a bias spring disposed between the
spring retainer and the valve element.
33. The fuel injection valve as claimed in claim 30, wherein the
bias spring includes a second end portion received inside the
stepped core tube, and a first end portion received in an inside
cavity formed in the valve element.
34. The fuel injection valve as claimed in claim 22, the larger
body section of the stepped tubular body extends from a second end
to a first end in a longitudinal direction of the fuel injection
valve; the smaller body section of the stepped tubular body extends
from a second end to a first end in the longitudinal direction; the
step portion of the stepped tubular body extends from the first end
of the larger body section to the second end of the smaller body
section so that a cross sectional size of the step portion
decreases gradually from the first end of the larger body section
to the second end of the smaller body section; and the reduced
portion is formed so that an annular space is formed between the
reduced portion and a second end portion of the smaller body
section of the stepped tubular body.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a fuel injection valve used
for injecting fuel to an automotive engine and the like.
[0003] 2. Description of the Related Art
[0004] Japanese Patent Unexamined Publication No. P2000-8990A
(2000008990) describes a fuel injection valve which is used for an
automotive engine and the like. Generally, a valve casing of the
fuel injection valve is made of magnetic metal material and the
like, and is shaped substantially into a tube. A valve body of the
fuel injection valve is displaceably inserted in an inner periphery
of the valve casing. In an operation period of the fuel injection
valve, a magnetic field generated by an electromagnetic coil may
act on the valve body by way of the valve casing, thereby opening
the valve body magnetically.
BRIEF SUMMARY OF THE INVENTION
[0005] It is an object of the present invention to provide a fuel
injection valve with accuracy in fuel injection amount improved by
stabilizing stroke of a valve body, wherein stabilization of the
stroke is effected by a general mechanical machining on a core
tube.
[0006] According to the present invention, there is provided a fuel
injection valve, comprising: a tubular body, a valve seat member, a
valve body, a core tube, a bias spring, and an electromagnetic
actuator. The tubular body is made of a magnetic material and
formed substantially into a tube. The tubular body has a first end
side and a second end side opposite to the first end side. The
valve seat member is disposed on the first end side of the tubular
body. The valve seat member is formed with a fuel injection port
and a valve seat surrounding the fuel injection port. The valve
body is displaceably disposed in the tubular body. The valve body
has a first end side defining a valve section which is detachably
seated on the valve seat of the valve seat member. The valve body
has a second end side, which is opposite to the first end side
thereof, defining an absorption section. The core tube is press
fitted into the tubular body. The core tube has a first end side
opposing the absorption section of the valve body in such a manner
as to form an axial gap interposed between the first end side of
the core tube and the absorption section of the valve body. The
core tube has a second end side axially extending in the tubular
body to a certain position on a way to the second end side of the
tubular body. The axially extending second end side of the core
tube has an outer periphery which is formed with a reduced diameter
section for increasing an accuracy in positioning the core tube
when the core tube is press fitted into the tubular body. The bias
spring is disposed in the tubular body, and biases the valve body
in a direction for closing the valve body. The electromagnetic
actuator is disposed at the tubular body. The electromagnetic
actuator forms a magnetic field between the absorption section of
the valve body and the core tube so as to allow the valve body to
open opposing the bias spring.
[0007] The other objects and features of the present invention will
become understood from the following description with reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0008] FIG. 1 is a longitudinal cross section of a fuel injection
valve, according to a first embodiment of the present
invention.
[0009] FIG. 2 is an enlarged cross section of the fuel injection
valve, taken along lines II-II in FIG. 1.
[0010] FIG. 3 is an enlarged cross section of the fuel injection
valve, taken along lines III-III in FIG. 1.
[0011] FIG. 4 is an enlarged cross section of an essential part of
the fuel injection valve in FIG. 1, showing especially a valve body
8's side of the fuel injection valve.
[0012] FIG. 5 is an enlarged cross section of the essential part of
the fuel injection valve in FIG. 1, showing especially a core tube
9's side of the fuel injection valve.
[0013] FIG. 6 is an enlarged cross section of a part in the
vicinity of a depth cut 10 in FIG. 5.
[0014] FIG. 7 is a longitudinal cross section showing a state
before assembling a tubular body 2, a valve seat member 5, the
valve body 8, the core tube 9, an electromagnetic coil 13, a
magnetic cover 14, and a couple core 16.
[0015] FIG. 8 shows a view similar to FIG. 5, but showing a core
tube 31 and the like of the fuel injection valve, according to a
second embodiment of the present invention.
[0016] FIG. 9 shows a view similar to FIG. 5, but showing a core
tube 41 and the like of the fuel injection valve, according to a
third embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0017] In the following, various embodiments of the present
invention will be described in detail with reference to the
accompanying drawings.
[0018] For ease of understanding, the following description will
contain various directional terms, such as, upper, lower and the
like. However, such terms are to be understood with respect to only
a drawing or drawings on which the corresponding part of element is
illustrated.
[0019] As is seen in FIG. 1 to FIG. 7, there is provided a fuel
injection valve applied to an automotive engine, according to a
first embodiment of the present invention.
[0020] There is provided a valve casing 1 constituting an outer
casing of the fuel injection valve. Valve casing 1 is constituted
of a tubular body 2 (to be described afterward), a magnetic cover
14, a resin cover 17, and the like.
[0021] Tubular body 2 constitutes a body section of valve casing 1.
Tubular body 2 is formed of a metal pipe and the like which is made
of magnetic metal material such as electromagnetic stainless steel.
As is seen in FIG. 1 to FIG. 7, tubular body 2 is formed
substantially into a stepped tube.
[0022] Tubular body 2 is constituted of a valve body receiver 2A, a
core tube mating section 2B, and a fuel passage section 2C. Valve
body receiver 2A is disposed on a first end side (lower in FIG. 1)
of tubular body 2. A valve body 8 (to be described afterward) can
be displaceably received in valve body receiver 8. Core tube mating
section 2B is unitedly disposed on a second end side (upper in FIG.
1) of tubular body 2A. A core tube 9 (to be described afterward)
can be inserted in core tube mating section 2B. Fuel passage
section 2C is disposed on a second end side (upper in FIG. 1) of
core tube mating section 2B, and is shaped substantially into a
tube having a diameter larger than that of core tube mating section
2B. Fuel passage section 2C has an inner periphery which forms a
fuel passage 3 extending axially up to valve body receiver 2A and
core tube mating section 2B. Valve body receiver 2A, core tube
mating section 2B, and fuel passage section 2C are arranged
substantially coaxial.
[0023] As is seen in FIG. 4, each of valve body receiver 2A and
core tube mating section 2B of tubular body 2 may have a
predetermined radial thickness t in a range from 0.2 mm to 10.0 mm,
more preferably, 0.2 mm to 3.0 mm. Moreover, valve body receiver 2A
and core tube mating section 2B are tubular bodies having
substantially the same diameter each other. Moreover, as is seen in
FIG. 1, there is provided a fuel filter 4 in fuel passage section
2C of tubular body 2. Fuel filter 4 can filter fuel which is fed to
fuel passage 3 from outside.
[0024] There is provided a valve seat member 5 which is
substantially tubular, and is inserted in an inner periphery on a
first end side (lower in FIG. 4) of valve body receiver 2A. As is
seen in FIG. 4, valve seat member 5 has a fuel injection port 5A
and an annular valve seat 5B. Fuel in fuel passage 3 can be
injected outward through fuel injection port 5A. Valve seat 5B is
formed substantially conical, and surrounds fuel injection port 5A.
Moreover, a valve section 8B of a valve body 8 (to be described
afterward) makes a movement such that valve section 8B can be
seated on valve seat 5B and spaced apart from valve seat 5B.
[0025] Moreover, valve seat member S can be inserted in the inner
periphery on the first end side (lower in FIG. 4) of valve body
receiver 2A of tubular body 2. Entire part of an outer periphery of
valve seat member 5 is welded to the inner periphery of valve body
receiver 2A via a weldment 6. Moreover, there is provided a nozzle
plate 7 on a periphery on a first end side (lower in FIG. 4) of
valve seat member 5. Nozzle plate 7 is fixed in such a position as
to cover fuel injection port 5A. Nozzle plate 7 is formed with a
plurality of nozzle holes 7A.
[0026] There is provided a valve body 8 which is displaceably
received in valve body receiver 2A of tubular body 2. Valve body 8
is constituted of a valve shaft 8C, a valve section 8B, and an
absorption section 8C. Valve shaft 8A is tubular, and extends
axially in valve body receiver 2A. Valve section 8B is
substantially spherical and is fixed to a first end side (lower in
FIG. 4) of valve shaft 8A. Moreover, valve section 8B can be seated
on valve seat 5B valve seat member 5 and spaced apart from valve
seat 5B. Absorption section 8C is made of magnetic metal material
and the like, and is integrated with a second end side (upper in
FIG. 4) of valve shaft 8A. Moreover, absorption section 8C is
substantially tubular, and can be slidably inserted in valve body
receiver 2A.
[0027] In a period when valve body 8 is closed, valve section 8B
can be kept seated on valve seat 5B of valve seat member 5 with a
bias force applied by a bias spring 11 (to be described afterward).
In this period, periphery on a second end side (upper in FIG. 4) of
absorption section 8C and core tube 9 oppose each other, defining
therebetween an axial gap S having a predetermined dimension, as is
seen in FIG. 4.
[0028] On the other hand, energizing an electromagnetic coil 13 (to
be described afterward) can generate a magnetic field H as depicted
by dashed lines in FIG. 4, to thereby allow absorption section 8C
of valve body 8 to be magnetically absorbed to core tube 9. With
this, valve body 8 can be axially displaced by a distance
equivalent to axial gap S against the bias force by bias spring 11.
Thus, valve body 8 can be opened in a direction A as is seen in
FIG. 4.
[0029] There is provided core tube 9 as a core member which is made
of magnetic metal material and the like and is shaped substantially
into a tube. Machining operations such as cutting, polishing and
the like carried out on the inner periphery and the outer periphery
of core tube 9 can form a stepped tubular body, as is seen in FIG.
7. A first axial side (lower in FIG. 7) of core tube 9 is a small
diameter section 9A, while a second axial side (upper in FIG. 7) of
core tube 9 is a large diameter section 9B. Moreover, core tube 9
has a gravity center G which is disposed on large diameter section
9B for ease of centerless polishing and the like (to be described
afterward).
[0030] Core tube 9 can be inserted in core tube mating section 2B
of tubular body 2 with a press fitting means. As is seen in FIG. 4,
core tube 9 can be fixed in core tube mating section 2B in such a
position that a first end face (lower in FIG. 4) of small diameter
section 9A opposes the second end face (upper in FIG. 4) of
absorption section 8C, defining therebetween axial gap S. In this
case, press fitting core tube 9 into core tube mating section 2B of
tubular body 2 causes the outer periphery of large diameter section
9B of core tube 9 to abrasively abut on the inner periphery of core
tube mating section 2B.
[0031] Large diameter section 9B of core tube 9 extends axially up
to a certain position on a way to the second end of tubular body 2.
More specifically, as is seen in FIG. 1. and FIG. 5, the second end
(upper) of large diameter section 9B protrude axially from core
tube mating section 2B toward inside fuel passage section 2C. In
addition, the second end of large diameter section 9B has an outer
periphery which is formed with a depth cut 10 (to be described
afterward).
[0032] There is provided depth cut 10 which is a reduced diameter
section defined on the outer periphery on the second end side of
large diameter section 9B of core tube 9. Depth cut 10 can be
formed through operations such as cutting, polishing and the like.
More specifically, as is seen in FIG. 1 and FIG. 5, depth cut 10
has a depth for example 100 .mu.m around entire circumference of
the second end of large diameter section 9B. Depth cut 10 can
increase frictional resistance (to be described afterward) of core
tube 9 against core tube mating section 2B, which frictional
resistance may be caused when core tube 9 is press fitted into
tubular body 2. With the increase in the frictional resistance,
accuracy in positioning core tube 9 press fitted into tubular body
2 can be increased.
[0033] Therefore, depth cut 10 extends axially from an end face of
large diameter section 9B of core tube 9 by a predetermined
distance. Depth cut 10 defines a depth cut end 10A which is
disposed in such a position that large diameter section 9B of core
tube 9 can define a length L1 (L1>0) relative to the second end
(upper in FIG. 5) of core tube mating section 2B into which large
diameter section 9B of core tube 9 is press fitted.
[0034] There is provided bias spring 11 disposed in tubular body 2.
There is provided a spring bearing 12 which is substantially
tubular, and is fixed inside core tube 9 through press fitting and
the like. Moreover, bias spring 11 can be compressedly disposed
between spring bearing 12 and valve body 8 inside core tube 9, to
thereby bias constantly valve body 8 in a direction of closing
valve body 8.
[0035] There is provided electromagnetic coil 13 fitting over the
outer periphery of core tube mating section 2B of tubular body 2.
Electromagnetic coil 13 can act as an actuator. Energizing
electromagnetic coil 13 by means of a connector 18 (to be described
afterward) can generate magnetic field H which is depicted by the
dashed lines, as is seen in FIG. 4. In addition, magnetic field H
can allow absorption section 8C of valve body 8 to be absorbed on
the first end face (lower in FIG. 4) of small diameter section 9A
of core tube 9, to thereby open valve 8 opposing the bias force by
bias spring 11.
[0036] There is provided magnetic cover 14 which is made of
magnetic metal material and the like, and is shaped substantially
into a stepped tube. As is seen in FIG. 4, magnetic cover 14 is
constituted of a small diameter tube 14A and a large diameter tube
14B. Small diameter tube 14A is welded to the outer periphery of
valve body receiver 2A of tubular body 2 via an annular weldment
15. Large diameter tube 14B is larger in diameter than small
diameter tube 14A, and is united with a second end (upper in FIG.
4) of small diameter tube 14A. Moreover, large diameter tube 14B
can cover electromagnetic coil 13 radially outside.
[0037] As is seen in FIG. 2, there is provided a couple core 16
fitting over the outer periphery of core tube mating section 2B of
tubular body 2. Couple core 16 is made of magnetic metal material
and the like, and is shaped substantially into an alphabetical C.
Couple core 16 can magnetically couple large diameter tube 14B of
magnetic cover 14 with core tube mating section 2B of tubular body
2. In cooperation with magnetic cover 14, couple core 16 can form a
magnetic path on the outer periphery of electromagnetic coil
13.
[0038] Magnetizing electromagnetic coil 13 can generate magnetic
field H, as depicted by the dashed lines in FIG. 4, along a closed
magnetic path which is constituted of valve body receiver 2A (of
tubular body 2), core tube mating section 2B (of tubular body 2),
absorption section 8C (of valve body 8), core tube 9, magnetic
cover 14, and couple core 16. With magnetic field H thus generated,
absorption section 8C of valve body 8 can be absorbed to the first
end (lower in FIG. 4) of small diameter section 9A of core tube
9.
[0039] On the other hand, there is provided resin cover 17 which is
so disposed, through resin molding and the like, as to cover
tubular body 2 and the second end (upper in FIG. 4) of magnetic
cover 14. As is seen in FIG. 1, resin cover 17 is fitted with
connector 18 for energizing electromagnetic coil 13. Moreover,
there is provided an O-ring 19 on the outer periphery on the second
end side (upper in FIG. 1) of tubular body 2 protruding from resin
cover 17. O-ring 19 can act as a seal member for sealing a space
defined between the fuel injection valve and a fuel piping (not
shown) or the like.
[0040] As is seen in FIG. 1 and FIG. 4, there is provided an
annular protector 20 disposed at valve body receiver 2A of tubular
body 2. Annular protector 20 is made of resin material and the
like, and protrudes radially outward from valve body receiver
2A.
[0041] Moreover, there is provided an O-ring 21 fitting over the
first end (lower in FIG. 1) of tubular body 2. O-ring 21 is
disposed between magnetic cover 14 and annular protector 20 in a
retained state. O-ring 21 can be used for example in the following
case:
[0042] When the first end of tubular body 2 mates with a boss
section (not shown) and the like disposed at an intake pipe of an
engine, O-ring 21 can seal an area defined between the first end of
tubular body 2 and the boss section.
[0043] Described hereinafter is operation of the fuel injection
valve, according to the first embodiment of the present
invention.
[0044] Before assembling the fuel injection valve, the inner
periphery and the outer periphery of core tube 9 are subjected to
machining operations such as cutting, polishing and the like. For
example, as is seen in FIG. 7, small diameter section 9A and large
diameter section 9B are formed at core tube 9, while entire
circumference of the outer periphery on the second end side of
large diameter section 9B is formed with depth cut 10 as reduced
diameter section.
[0045] Then, thus formed core tube 9 is press fitted into core tube
mating section 2B of tubular body 2, while electromagnetic coil 13
and magnetic cover 14 are allowed to fit over tubular body 2. Then,
resin cover 17 is allowed to fit over electromagnetic coil 13 and
magnetic cover 14 by means of resin molding and the like. Moreover,
valve body 8, bias spring 11 and the like are mounted in valve body
receiver 2A of tubular body 2. Thereafter, valve seat member 5 is
inserted in body receiver 2A of tubular body 2, and then welded.
With the steps described above, the fuel injection valve can be
assembled.
[0046] When the fuel injection valve is mounted on the automotive
engine and the like, the fuel can be supplied in fuel passage 3 of
tubular body 2, from the fuel piping and the like which is
connected to the second end (upper in FIG. 1) of tubular body 2 by
way of O-ring 19 and the like. Allowing connector 18 to energize
electromagnetic coil 13 can generate magnetic field H, as is seen
in FIG. 4. Thus generated magnetic field H can pass between
absorption section 8C (of valve body 8) and core tube 9.
[0047] Thus, valve body 8 can be magnetically absorbed by core tube
9, and therefore is displaced axially opposing the bias force by
bias spring 11. As a result, valve section 8B of valve body 8 can
be spaced apart from valve seat 5B of valve seat member 5, to
thereby open valve body 8. With this, the fuel in fuel passage 3
can be injected from fuel injection port 5A toward the intake pipe
and the like of the engine.
[0048] The fuel injection valve to be assembled in the manner
described above may have the following constitution:
[0049] Axial gap S between valve body 8 and core tube 9 is secured
larger than its predetermined set value, in view of welding error
and the like which may be caused when valve seat member 5 is welded
in valve body receiver 2A of tubular body 2.
[0050] After the fuel injection valve is assembled, axial gap S is
subjected to adjustment to its predetermined set value by axially
press fitting again core tube 9 into core tube mating section 2B of
tubular body 2.
[0051] In the above adjustment of axial gap S, core tube 9, as the
case may be, makes a return movement with an error for example
about several tens of .mu.m in core tube mating section 2B of
tubular body 2. The above error (return movement) is attributable
to residual stress and the like which may be caused when core tube
9 is press fitted axially with the press fitting means. The above
error (return movement) may increase axial gap S between absorption
section 8C (of valve body 8) and core tube 9. Even if such increase
in axial gap S is minor, stroke of valve body 8 will vary, thereby
deteriorating accuracy in controlling fuel injection amount.
[0052] According to the first embodiment, accuracy in positioning
the core tube 9 in tubular body 2 can be improved by allowing depth
cut 10 to increase frictional resistance which may be caused when
core tube 9 is press fitted into core tube mating section 2B of
tubular body 2. Hereinabove, depth cut 10 is the one that is formed
around the entire circumference of the outer periphery on the
second end side (upper in FIG. 1 and FIG. 5) of large diameter
section 9B of core tube 9.
[0053] More specifically described as follows: High-accuracy
polishing is carried out on the outer periphery of large diameter
section 9B, so that press fitting large diameter section 9B (of
core tube 9) into core tube mating section 2B (of tubular body 2)
can cause frictional abutment between the outer periphery of large
diameter section 9B and the inner periphery of core tube mating
section 2B. Press fitting large diameter section 9B (of core tube
9) into core tube mating section 2B (of tubular body 2) may cause a
force in a direction B toward tubular body 2, as is seen in FIG. 6,
in other words, the force in direction B is for increasing
diameter. On the other hand, press fitting large diameter section
9B may cause a force in a direction C toward large diameter section
9B, in other words, the force in direction C is for decreasing
diameter.
[0054] The thus caused force in direction B for increasing diameter
and the force in direction C for decreasing diameter can be in
balance with each other on the outer periphery of large diameter
section 9B of core tube 9. In core tube mating section 2B's
position corresponding to depth cut 10, however, only the force in
direction C may be caused, in other words, the force for decreasing
diameter. Thereby, in the vicinity of depth cut end 10A of depth
cut 10, core tube mating section 2B of tubular body 2 may partly
cause an elastic deformation depicted with imaginary lines, as is
seen in FIG. 6, thereby causing a wedge force in a direction D.
[0055] As a result, at depth cut end 10A of depth cut 10, the above
wedge force in direction D can cause an anchor effect (wedge
action) on large diameter section 9B of core tube 9, to thereby
increase the frictional resistance between tubular body 2 and core
tube 9. In addition, the wedge force in direction D may cause the
elastic deformation of core tube mating section 2B such that part
of core tube mating section 2B can slightly engage with depth cut
end 10A of depth cut 10. In sum, the anchor effect can control the
return movement (attributable to the residual stress and the like)
of core tube 9 in direction E as is seen in FIG. 6.
[0056] In sum, accuracy in positioning core tube 9 in tubular body
2 can be thus improved, to thereby allow axial gap S between valve
body 8 and core tube 9 to be adjustable to the predetermined set
value. In addition, magnetic field H generated by electromagnetic
coil 13 can pass between valve body 8 and core tube 9, to thereby
allow valve body 8 to be opened at an adjusted stroke (equivalent
to axial gap S). In sum, stable fuel injection amount can be
controlled.
[0057] According to the first embodiment, forming depth cut 10
around the entire circumference on the second end side of large
diameter section 9B of core tube 9 by means of general machining
operations can set a constant stroke of valve body 8, thereby
improving accuracy in the fuel injection amount.
[0058] Gravity center G of core tube 9 disposed on large diameter
section 9B as is seen in FIG. 7 can allow polishing of the outer
periphery of large diameter section 9B of core tube 9 without the
need for preparing special jigs and the like for sustaining core
tube 9. Thus, centerless polishing known as easy machining can be
adopted, to thereby allow efficient finishing and the like.
[0059] As is seen in FIG. 8, there is provided a fuel injection
valve applied to the automotive engine, according to a second
embodiment of the present invention.
[0060] In the second embodiment, parts and sections substantially
the same as those according to the first embodiment are denoted by
the same numerals, and repeated descriptions are omitted. The
feature of the second embodiment is a chamfer section 32 as a
reduced diameter section around an outer periphery on a second end
side (upper in FIG. 8) of a core tube 31.
[0061] Like core tube 9 according to the first embodiment, there is
provided core tube 31 which is constituted of a small diameter
section 31A and a large diameter section 31B. Chamfer section 32 as
the reduced diameter section can be formed by tapering an outer
periphery on a second end side (upper in FIG. 8) of large diameter
section 31B. Chamfer section 32 is so formed as to extend to a
position defining a length L2 (L2>0) relative to the second end
of core tube mating section 2B of tubular body 2.
[0062] In sum, according to the second embodiment operations and
effects substantially the same as those according to the first
embodiment can be caused. Especially, according to the second
embodiment, chamfer section 32 can be formed with ease by simply
tapering the outer periphery on the second end side of core tube
31, thereby further facilitating machining operation.
[0063] As is seen in FIG. 9, there is provided a fuel injection
valve applied to the automotive engine, according to a third
embodiment of the present invention.
[0064] In the third embodiment, parts and sections substantially
the same as those according to the first embodiment are denoted by
the same numerals, and repeated descriptions are omitted. The
feature of the third embodiment is an annular groove 42 as a
reduced diameter section around an outer periphery on a second side
(upper in FIG. 9) of a core tube 41.
[0065] Like core tube 9 according to the first embodiment, there is
provided core tube 41 which is constituted of a small diameter
section 41A and a large diameter section 41B. A plurality of
annular grooves 42 as the reduced diameter section can be formed in
such a manner as to be spaced apart axially from each other in
positions for frictional abutment between an outer periphery (of
large diameter section 41B) and core tube mating section 2B. In
addition, each of annular grooves 42 has a cross section shaped
substantially into a Japanese katakana character (rectangular
character), for example, with groove width of about 100 .mu.m and
groove depth of about 100 .mu.m.
[0066] In sum, according to the third embodiment operations and
effects substantially the same as those according to the first
embodiment can be caused. Especially, according to the third
embodiment, the plurality of annular grooves 42 are formed on the
outer periphery of large diameter section 41B, thereby effecting
the anchor effect (wedge operation) and further improving accuracy
in positioning core tube 41 in tubular body 2.
[0067] Although the present invention has been described above by
reference to three embodiments, the present invention is not
limited to the three embodiments described above. Modifications and
variations of the embodiments described above will occur to those
skilled in the art, in light of the above teachings.
[0068] More specifically, according to the third embodiment,
annular groove 42 formed on the outer periphery of large diameter
section 41B of core tube 41 is plural in number. The present
invention is, however, not limited to this. For example, annular
groove 42 can be singular in number. In addition, the cross section
of annular groove 42 may not necessarily be shaped substantially
into the Japanese katakana character (rectangular character).
Instead, the cross section of annular groove 42 can be a
semicircle, an alphabetical U, an alphabetical V, and the like.
[0069] The entire contents of basic Japanese Patent Application No.
P2001-395543 (filed on Dec. 27, 2001 in Japan) of which priority is
claimed is incorporated herein by reference, in order to take some
protection against mis-translation or omitted portions.
[0070] The scope of the present invention is defined with reference
to the following claims.
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